Bag tube and method of making same



Nov; 3', 1936.-

T. O. BANGRCFT BAG TUBE AND METHOD OF MAKING SAME 2 sheets-sheet 1yFiled 0G12. 18, 1934 .fc-9. 5 @w M am Nov. 3, 1936. T. o. BANcRoFT BAGTUBE AND `ME'II-IOD OF MAKING SAME VFiled om. 18, 1954 2 shets-sheet 235, 62.3'. wmlyf www Patented Nov..` 3, 1936 PATENT OFFICE BAG TUBE ANDMETHOD OF SAME ` Thomas 0. Bancroft, Monroe, La.

Application October 18, 1934, Serial No. 748,855

3 Claims.

My invention relates to paper bags and their manufacture.

In the manufacture of paper bags for the carbon black industry,difficulties have been encoun- 5 tered that do not occur normally in theuses of paper bags. Carbon black is such a finely divided substance thatit will flow or rather sift through open crevices in the bottoms ofpaper bags Whereas coarser materials would not.

Numerous attempts have been made tol overcome these small leaks. Forexample, patches of paper have been glued onto the bottoms of paper bagsand false bottoms have been pasted on them to prevent leaking. Theseattempts at solving the difficulty have not been satisfactory,principally because of the increased cost f manufacture.

To overcome leaks in paper bag bottoms, I have directed my inventivethought into redesigning the paper bag bottom itself. v

My inventive ideas set forth in the instant application are shown anddescribed in. this application to multiple ply satchel bottom bags of atype popular in the carbon black industry. However, I do not limit myinvention to this type of bag only because` the features of my inventionare applicable to other types of bags for uses wherever any finelydivided material is to be confined.

An important object of my invention is to pro- 30 vide a sift-proof bag.

A further object of lmy invention is to provide a method of forming thebottom of abag to prevent it from leaking.

A further object of my invention is to provide 5 a method of gluingtogether plies of bag material preparatory to the formation of a bag.

Other objects and advantages of my invention will be apparent l'duringthe course of the following description.

In the accompanying drawings, forming a part of this description and inwhich like numerals are employed to designate like parts throughput thesame, Fig. 1 is a plan view illustrating a gluing step in the formationof my improved bag;

Fig. 2 is a view illustrating a tube forming step in the formation of myimproved bag;

Fig. 3 is a View illustrating a bottom slicing step in the formation ofmy bag;

Fig. 4 is a view illustrating the first bottom folding step in theformation of my improved bag,

Fig. 5 is a view illustrating a bottom scoring step in the formation ofmy improved bag;

Fig. 6 is a view illustrating the placing of the gottom glue tab in theformation of my improved Fig. 7 is a view illustrating the first bottomclosing operation in the formation of my improved bag; I

Fig. 8 is a view illustrating the second bottom closing operation, thelast step in the formation of my improved bag.

Fig. 9 is a plan view of a multiple ply bagl embodying my invention.

I In the drawings, wherein,\for the purposes of illustration, is shown apreferred form of my invention, numeral l designates the tube portion ofa bag and numeral 2 designates, generally, the bottom portion.

Applicant has noticed that, in multiple ply wall bags, finely dividedmaterials have a way of working between the plies of the bag materialexposed on the inner side ofv thebottom. The finely divided materialthen finds its way out of the bag between the plies through openingbetween the plies on the under side of the bags bottom.

To prevent this type of leak, applicant, in the process of making hisimproved type of bag, fastens plies A and B together by means of acontinuous glue tab I0 (seeFig. 1). The laminated material is thensevered on line I3 close to and along side the glue tab I0. The gluedends of the plies are later folded into the bottom of the bag.

In the gures illustrating the steps in the process of making a bagaccording to my invention, arrows are used to indicate the direction oftravel the bag material would take if the operations were performed by acontinuous type bag making machine. 3

In the formation of a multiple ply wall tube for bag construction, thefirst step is the placing of-the tab Il) between the plies of bagmaterial. This is accomplished by means of a suitable glue applyingmeans G. The glue tab ID is shown formed with U shaped portions II. Thetab is made wider at the center. A notch space l2 is left in the centerportion of the glue tab. After the glue tab I0 has been applied to oneof the plies, the two plies are brought together land stuck. 'Ihemultiple layer sheet is then outv l close to the glue tab by means of asuitable cutting means N. Where more than` a double ply bag is desired,additional plies may be superimposed and fastened together by employingad- A ditional glue tabs between'the added bag material. (See Figure 1).

After the plies have been glued together, the laminated sheet is formedinto a tube and fiattened (see Figure 2), so as to bring pairs of the 55plies of U shaped portions II of' the glue tab I0 together. (See Fig.2.) It is by means of the U shaped portions of the glue tab I 0 thatclean paper is left for the bottom cutting knives K to cut through. Thisfeature prevents the bottom cutting knives from gumming up with glue.

In Fig. 3, the bottom slicing step is shown. In standard bag makingmachines, the bag is grabbed at this stage by means of a gripper P,generally provided with three pins which are passed through the tube.'I'he notch I2 was purposely provided in the glue tab l0 to leave aclean paper space for the center pin to puncture.

The position of the outer grabbing pins allows them to puncture parts ofthe clean paper spaces Within the U shaped sections of the glue tab I0.

After the tube I has been cut as shown in Fig. 3, the 4 tongues of paperformed in the end of the tube, by the cuts through the end of theflattened tube, may be folded together with parts of the tube properinto a bottom to complete the bag in accordance with standard practicesin bag making, well known to those skilled in the art of bag making.

However, I have gone further in my method of bag making, in that I havemodified andimproved the bottom folding and bottom gluing operationsthemselves.

In Fig. 4, the two side tongues 2| formed in the tube by the cuts,together with parts of the tube stock, are shown creased over toward thecenter line of the tube. Numeral 22 designates the forward tongue andnumeral '23" designates the rear tongue.

In the next operation, the bottom surface is scored on lines 24 tofacilitate folding operations. These scores determine the shape and areaof the bottom of the finished bag.

In the formation of the Satchel type bottom on va bag, part of the tubestock, as well as the tongues, must be folded into the bottom.

In a bag of this type, a finely divided substance will find its way outof the bag between the folds of the bottom, if not prevented. 'Ihepoints V (see Figures '7, 8, and 9) mark, in the Satchel type bags,openings through which finely divided materials find their way out ofthe bag between the folds of the folded tube stock brought into thebottom of the bag.

To overcome this difficulty, applicant allows for greater distances Xbetween his score lines 24 and the openings V than the distances Ybetween the center line ZZ, and the score lines 24, so that the opening`V will fall beyond the center line Z-Z, when the final folds are madein the formation of the bag. (See Fig. 5.) 'Ihis method of foldingpermits the openings V of the rear flap 23, when folded, to be latercompletely covered by, and sealed under, part of the bag stocklconstituting the forward -flap 22, the last flap to be folded.

This feature of bottom construction may be.

of the bag trade for particular sizes of bags predetermines thelocations of these score lines. Therefore, your applicant, to accomplishhis end, resorted to the method of varying the distance between the cutsC. An abundance of glue is applied to the forward flap at its points Vtoy assist in sealing the same.

To accomplish my purpose outlined above in Satchel bottom bagconstruction, I fold the side flaps in the conventional manner employedin the manufacture of this type of bag. (See Fig. 4.) The scoring step(Fig. 5) is also carried out according to standard practice tofacilitate the final folding operations to follow. In the glue tabbingstep, next to follow (see Fig. 6), standard practice is varied from inthat the forward and rear tongues 22 and 23, respectively, are maderelatively narrower than in standard practice. This fact necessitatesthe using of relatively narrower U-shaped blue tabs T.

Next in sequence is the first -nal folding operation, see Figure 7. Herestandard practice is varied from in that the entire length of the cutsC, including the openings V, are folded to lie beyond the center lineZ-Z of the bottom of the bag.

The next and last step in the formation of the bottom is the finalfolding operation. (See Fig. 8.) Here the final closing flap 22, theforward fiap, is folded to completely cover the entire cut lengths C andopenings V of the previously mentioned rear flap 23. Thus the bag iscompleted.

Fig. 9 shows the bottom features of the above described inventionapplied to a multiple ply wall bag, vcomprising tube portion la, andbase portion 2a. 5a designates points of glue used to lightly tacktogether the plies of bag material near the bags mouth to make the bagopen properly. In the formation of the bottom of this bag, the steps asoutlined in connection with Figures 4 to 8 are carried out the same asif only a single-f position for cuts and the step of brlnging'to-ygether the sheets of bag material and sticking the same together afterthey glue tab has been placed between them.

2. The method as defined in claim 1 wherein the glue tab includesvariations to allow for cutting and puncturing of the combined sheets intube form.

3. A multiple bag tube comprising plies of bag material joined crosswiseby one or more glue tabs, the tube being slit at one end, portions ofthe glue tabs extending crosswise of the tube below the slits.

THOMAS O. BANCROFI'.

